The intake manifold will be different in that its a lot longer and curved. Redline at 8000 instead of 6800. valve cover says vtec on it. Also the gsr has a frot strut and a rear sway. Not sure if the ls has the rear sway also though.

The best and easiest way to tell if the car is a geniune GSR or not would be to look at the VIN. If the car is a coupe, than the fourth, fifth, and sixth digits of the VIN should be "DC2." If the car is a sedan than those digits should read "DB8." Also, the eighth digit of the VIN should be either 8 or 9, depending on whether the car has leather seats or not.